Unless otherwise indicated herein, approaches described in this section are not prior art to the claims listed below and are not admitted as prior art by inclusion in this section.
In New Radio (NR), uplink grant-free transmission using configured grants or transmission without dynamic scheduling is proposed to reduce the latency of ultra-reliable and low latency communications (URLLC) services. A user equipment (UE) may be configured to transmit its uplink data on some radio resources without requiring a prior request (e.g., scheduling request (SR), random-access channel (RACH) request or buffer status report (BSR)) to improve its transmission latency. In the transmission and reception without dynamic scheduling, the network apparatus may pre-configure specific radio resources (e.g., time and frequency resources) for the UE to perform the transmission. These specific radio resources may be potentially shared by a plurality of UEs. Consequently, collisions or conflicts of the transmissions may happen among the plurality of UEs.
Accordingly, one important performance target for the contention based grant-free transmission may be lowering the collision rate. As more UEs try to transmit uplink data simultaneously on contention based grants, the probability of collisions may be increased. The transmission reliability and latency may also be degraded. Therefore, in order to meet the service requirements targeted by the contention based grant-free transmissions, it is needed to minimize the collisions.